Electrocardiograph



Jan. 15, 1957 w. E. GlLsoN ETAL 2,777,747

ELECTROCARDIOGRAPH original Filed May 2, 195o 4 Sheets 5heet 1 Jan. 15, 1957 W- E-y G11-SON ETAI- 2,777,747

ELECTROCARDIOGRAPH 4 Sheets-Sheet 2 Original Filed May 2, 1950 @NN vvN,

Jan. 15, 1957 w. E. GlLsoN ErAL 2,777,747

ELECTROCARDIOGRAPH Original Filed May 2, 1950 4 Sheets-Sheet 3 Jan. 15, 1957 w. E. GlLsoN ETAL 2,777,747

EYLECTROCARDIOGRAPH Original Filed May 2, 1950 4 Sheets-Sheet 4 United States Patent() ELECTROCARDIOGRAPH Warren E. Gilson, Madison, and Sherrill K.Rasmu ssen, Milton, Wis., assignors to The iBnrdick'Corporation, Milton, Wis., a corporation of Delaware Original application May 2, 1950, Serial No. 159,608, now Patent No. 2,674,992, dated April 13, 1954. Divided and this application July v31, 1953, lSerial No. 371,574

3 Claims. (Cl. 346-136) The present invention relates to electrocardiographs primarily although certain aspects of the invention may be applied to other devices where similar problems are encountered.

The present application is a division of our-application Serial No. 159,608, tiled May 2, 1950, for Electrocardiograph, now vPatent No. 2,674,992, issued April 13, 1954.

Essentially an electrocardiograph is a heart diagnostic instrument through which a tape is pulled continuously when the device is in operation and upon which tape a curve is drawn to indicate substantially the electric potential changes between diiferent parts of the body-due to the heart action.

Essential elements of such a device, therefore, are the tape storing, handling and pulling mechanism, the tape marking device, a high gain amplifying system `for'actuating the marking device, a plurality of electrodes for attachment to the patient, together with their attendant cables, and a switching arrangement for connecting these cables in different combinations to the amplier. Most of these components are assembled within a chassis and a case is provided to house the equipment.

One of the objects of the present-invention is to provide Y such an instrument with an improved tape handling mechanism which is particularly advantageous whenusged with a paper base tape of the type now commonly employed.

Still another object is to provide a novel and convenient tape handling and pulling mechanism which is e'asy to thread. l

Other objects and advantages will become apparent from the following description of a preferred embodiment of our invention which is illustrated in the accompanying drawings, in which:

Fig. l is a side view of an electrocardiograph embodying the present invention, the mechanism being removed from the case so as to show its essential structure. In this View portions of the apparatus, such as the amplifier,

.for instance, have been eliminated since their construction is not essential to an understanding of the present invention;

Fig. 2 is a plan view of a portion of the tape used by and marked in the machine shown in Fig. l; l

Fig. 3 is a top view of the electrocardiograph illustrated in Fig. l;

Fig. 4 is a vertical transverse sectional view whichmay be considered as taken substantially along thevvline 4-4 of Fig. l in the direction indicated by the arrows; l

Fig. 5 is a longitudinal vertical sectiona1 view which may be considered as taken substantially along the line 5 5 oi Fig. 3 in the direction indicated by the arrows;

Fig. 6 is a top fragmentary view drawn to larger scale of a portion of the mechanism illustrated in Fig. 3 so as to show its construction and operation in greater detail;

Fig. 7 is a vertical fractional sectional view of a portion of the mechanism drawn to large scale so as to illustrate a `portion of the linkage mechanism for markingcjertain indicia Aupon the tape 'passing through the' device;y and iFig. 8 is a detail vertical longitudinal sectional view which maybe considered as taken substantially along the line 8--8 of'Fig. l in the direction indicated by the arrows. The electrocardiograph which forms the subject of the present invention has its working mechanism largely en- :closed within and supported by rectangular generally open described.

Within this frame and at one end thereof, the left end as seen in Figs. l and 3, there is a separate subframe upon which the galvanometer and tape pulling and handling mechanism is mounted. This subframe is made up of a rigid Vcast base 20 somewhat less than half the width of the bottom plate 10 which is fastened by screws thereto. The casting 20 carries at one side an upstanding plate 22 about half as long as `the chassis at about the middle thereof. This plate is arranged near one end of the frame andextends from top to bottom. It, together with a similar but longitudinally shorter outside plate 24, bolted to theother side of the subframe 2t), acts to support thetape handling mechanism, as an integrated rigid structure.

A horizontally and transversely disposed tape supporting tube 26 is mounted upon the vertical plate 22 low down and toward the left, as seen in Figure l. Itvhas-an external diameter slightly smaller than the internal `diameter of the spool 27 upon which a roll 28 of recording tape 29 is wound so that the spool of tape maybe easily siipped over the tube 26. Once in position it is retained 'tape spool 27.

From the top of the roll, the paper tape A29 passes rearwardly over a horizontal, transversely disposed pin 32. This pin projects from and is tiXed to the plate 22. The pin per se is best observed in Fig. 4 where it will beseen that -its outward end has a head 34 of a diametersomewhat larger than its stem, while its inner end similarly is provided with a collar or enlargement 36 of approximately the same diameter as the head 34. The stem portion of the pin 32 between the collar 36 and the head 34 is slightly longer than the width of the paper tape 29 which passes thereover.

vof its side edges bent over at approximately right angles to Aform flanges 42 to give it greater stiffness. It rests against the upper surfaces of the head 34 and collar 36 near its right hand end and has this extremity bent downwardly to form a tab 44 which'lies just beyond the pin 32. The paper tape is therefore caused to pass over the pin 32 and thence downwardly around the end rof the tab 44, and thence sharply upwardly in a manner to be pointed out presently in greater detail.

l The left hand end of the keeper 40 or more properly these ends of its side flanges 42 are pivoted to a horizontal cross pin 46 which has its ends fixed in the vertical plate 22, and an L-shaped subframe member 48 which is supported in a manner to be discussed presently. The tensioner 4tl is therefore free to pivot upwardly and downwardly about the pin 46. At its left hand end beyond the cross pin 46 the end portion of the plate 40 is bent downwardly at about right angles and thence to the right to form al transverse spring seat or abutment .arrasar Sii. A pai.: of side by side coil springs 52 have their left ends fixed to a transverse rod 54 also secured to the vertical plate These springs pass downwardly around the abutment Sil and thence upwardly where their ope posite ends 56 are hooked through openings in the plate l0 well beyond the cross pin 46. Since these springs are under tension they will resiliently hold the free end i4 of the paper tensioner 4l@ against the pin 32. A transverse pin 57 projects from the rod 54 and serves as a handle to rotate the rod 54 to adjust the tension of the springs 52 and hence the paper 'speed which should be constant with very narrow limits.

An L-shaped sheet metal bracket 58 has one end bent over and secured to the lower surface of the plate 40 as by rivets 65B. This bracket extends downwardly .in a plane parallel to the backing plate 22 from the tensioner 38 and thence curves toward the right as seen in Fig. into a position somewhat beyond the pin 32,r

and is provided at its end with a transverse headed pin 62. This headed pin 62 lits a longitudinal slot 64 in a downwardly extending sheet metal arm 66 which is provided for pulling upwardly on the pin 62 so as to lift the end of the arm 58 and thence to raise the tab 44 of the tensioner 33 into a position well above the cross pin 32, the purpose being to facilitate threading of the tape 29 through the tape pulling mechanism as will appear subsequently.

The L-shaped side lsupport bracket 418, previously referred to, is in the same plane as the side plate 24 and may be considered as an extension of this plate with a curved slot 49 formed therebetween. lt is disposed with one arm of the L. in a generally horizontal position, this portion of the arm being fixed by screws 70 to a pair of parallel transverse rods 54 and 68 which are `secured at their opposite ends to the vertical plate 22. The right hand portion of the bracket 4d, indicated by the numeral 72, inclines upwardly toward the right and has its upper end secured by a pair of screws 74 to the outward end of a horizontal transversely extending rectangular bar 76 (Figs. 4 and 3) anchored at its inner end to the plate 22.k This transverse bar '76 also carries a dull knife edge 78 secured thereto in face to face relation with the thin edge uppermost.

The tape 29 is passed over this edge and thence downwardly around a driving or pulling roller 8@ which will be described more specifically subsequently. At present it is sufficient to note that it is journaled to rotate about a horizontal transverse axis which extends between the vertical plate 22 and the bracket 43, and that the rotating axle for the roll Sil passes through the plate 22 where it is connected to the output shaft of an electric motor and `speed reducing gear box unit S2 mounted upon the back of the plate 22. This motor is of the synchronous type and drives the roll till at a constant speed of 30 revolutions per minute.

The tape is pressed against the driving roll 8@ by an idling or clamping roll or roller 3d which is comprised of a layer of soft rubber formed about an axle 86 journaled at its ends in a pair of overhanging arms 3S. These ar-ms which are parallel are formed of sheet metal and are spaced apart a distance somewhat greater than the width of the paper tape 29. They extend from the idling roll 84 in a generally left hand direction for a short distance and thence upwardly and toward the right to a position somewhat above the knife edge 7S and thence to the right and downwardly such that their opposite ends are pivoted to a cross pin 96 which extends between the plates `22 and 24. The two generally J-shaped arms Sure cross braced at intervals to maintain spacing and approximate alignment by means of transverse rods 92, 94 and 96. One of these rods 9d, which is spaced somewhat to the right of the top of the knife TS, is formed of an electrical insulating material7 since it is also used to manipulate a pair of electrically heated styluses and might short circuit the stylus leads were it formed of metal. The construction and arrangement of these styluses will be pointed out presently.

The pivotal connection between the arms 88 and the rod 9i) is formed by a pair of `slots 9S in the right hand ends of the arms 88 which straddle the rod 9d. The slots have a width to fit the rod 9d and a length such that the arms 86 and roller 84 can move backwardly and forwardly as well as pivotally relative to the rod 9i?. These slots incline upwardly and to the left so that as the right hand ends of the arms S8 slide toward the right, they also move downwardly with respect to the rod 91).

At a point somewhat below and to the left of the rod 90, the arms S8 are connected to the ends of a pair of coil springs 100 which extend downwardly to the right. and have their opposite ends attached to screws i102 fixed in the plates Z2 and 24. The angle of action of these springs is such as to tend to cause the free ends of the arms 3S, that is the ends attached to the idling roll da, to be swung downwardly and to slide toward the right under the influence of these springs. The extreme lower free ends of the arms 8S below the roll tid are bent sharply outwardly to form tabs or guides lil@ which rest against the sides of a pair of short transverse pins or guides 166 fixed to the plates 22 and 48. The action of these tabs against the pin lille limits the downward movement of the idling roll 5d such that further action of the springs 100 causes a sliding movement of the arms toward the right, thus squeezing the idling roll da against the face of the paper tape opposite the driving roll bd.

It will be noted with reference to l that the orientation of the roller support guides .lila in relation tothe roller support arms 8S and to the stationary guides ldd is such that movement of the clamping roller 3ft in the Vicinity of the pulling roller cltl is constrained tu a predetermined direction making a large acute angle relative to a straight line extending through the axes of both rollers. Hence, upon application of a force to the clamp`- ing roller 84 in this predetermined direction, the guides 164 and 106 force the clamping roller toward the pulling roller 80 with a wedging action that multiplies the force with which tape is clamped or gripped between the rollers. It is also noteworthy that the lines of action of the springs 190 on the arms 8S malte acute angles with the predetermined direction referred to above thus rendering large components of the spring forces available for wedging the clamping roller 3d against the pulling roller 8b. Also, the spring produced reaction of the pin 90 on the arm structure defining the slots 93, Fig. 5, is transmitted through the arms 38 to further wedge the clamping roller 84 against the pulling roller di).

After the tape has passed between the rolls 80 and 84, it crosses a small table MBS supported by the bars 54 and 68 previously referred to which directs the tape to the outside of the machine at lli. The tape is prevented from bunching up on the table ldd by an overlying transparent plastic guard lill which is hinged at its outward end to pins 114 carried in small brackets M6 fixed to the top of the table Mtl. Because of this hinge connection the inner end of the guard may be tilted upwardly to facilitate threading the tape thereunder after which it may be pushed down into the position shown in Figs. 5 and 2, for instance. As shown in Fig. 3 the central portion of the guard 112 in the region of its outward end may be cut away as indicated at il@ to permit free insertion of the operators linger to facilitate alignment of the end' of the tape across the table and beneath the guard M2.

This tape handling mechanism insures the tape moving smoothly at proper speed and since the tensioning apparatus works against an intermediate portion of the tape, the tension is not affected by the size of the roll and thus gives more accurate control than is customary.

To the right and slightly below the insulated spacer 94 a shaft 120 extends transversely between the vertical plates 22 and 24.l It is journaled in these plates and is provided with a knob 122 at its outward end beyond the of contact with the spacer 94; This camming'surface is` generally spiral inform so that as theshaft 120 is rotated a clockwisev direction, the ca mm'ing' surfacev 128 is brought'against the spacer 94and-with continued 'rotation forces the spacer 94 upwardly and to 4the leftl T-heeX- treme'end of this `carriming surface is formedto provide a -stop130 which isbrou'ght against theunder surface `0f thespacer 94-l and limits'the rotational'tra'vel of the cam 124.L

The'angle made with thehorizo'ntalb'y'a line through *the spacer 94 andthe rotatable shaft-120'is lessthan that rfnideby` th'eespring 100,- with theresult that when' the khob122 is rotated ina clockwise direction andthe-cam surface 128` is' brought againstthespacer 94, l further rotation at'fistcau`ses"the"arms`8'8 and rollerf84'to be shifteditowardthe left without the" rollerY being? appref ciablyy lifted. This movement is accommodated byfthe slot 98 which embraces the pin 90. After a predetermined degree of travel ofthe arms 88 to the' left the'lower ends of th'eslo'ts l9Simping'eagainst the pin90 and further travel of the arms 88 to the left is inhibited. Upon-additionallrotation of the knob 122 the'cam 124'liftsthe spacer'94' arcuately, the center of rotationbeing-.at the pin 91).Y When thestop'13tl is brought against the spacer 94" the `arms SS'havebeen 'lifted into the phantom'line position-'shown in'Fig. 5. Since'the portion of `the-cam mining surface 128 immediately adjacentthe stop 130- is flat'for slightly reentrant with respect to the shaft'120'; the cam is locked with the arms`88 in the uppermost position. That is, once thel arms have been raised andthe stop-'130 has been'brought against-'thespacer 94; thevsprin'gA 100 will not return the arms S8 to their lowermost position. This over-center action of the cam enables the -knob 122 to be released after'the arms are raised so that both hands can' be used for threadingthe tape through' the machine.

It will be seen that lthe idling roller 84 presses the tape 29 against the ldriving roll S0 well below its center line, thereby'insuring good frictional driving engagement `and that the linkage just described automatically insures that simple rotation of the knob 122 in a clockwise direction will-shift the idling roll 84 approximatelyA horizontally to the left well clear of'the roll 80 before lifting it, thereby preventing binding and scufng of the tape. Y l

Therock-shaft 120 also carries an arm132'whichinclines downwardly and to the left and at its lower end is connected by a pin 134to the upper end of the link 66 previously referred to.

Y Thus it will be seen that whenthe knob 1,22 is rotated in a clockwise direction so as to cause the carn124'to lift the roller 84, this rotational movement of the shaft 120l also causes the arm 132 to lift the link 66. After this link has been lifted a short distance the lower end of the slot 64 is brought against the headed pin 62 so that ,continued rotation'of the shaft 120 causes the link 66 to lift the right hand end of the arm 53, thereby lifting the tensioner 3S away from the cross pin 32. In its uppermost position the connection betweenthe arm 132 and link- 66 passes the center line of the shaft 120 so that the`action of'the springs 52 do not tend to reverse the rotation' of the knob 122 when it is released. To permit this the upper end of the link 66 is offset somewhat to the right so as to avoid its impinging against the shaft120.

As best seen in Fig. 3, the right hand end of the base casting 20 supports a galvanorneter 136 which isenerized by 'the' amplifier circuit of the device. The responsive element'of this galvanometer is connected to a rotatable shaft 138 `which projects vertically at the top ofthe galv'anometer and is there connected to a stylus, indicated generally' by the numeral 146.' j

This stylus consists of two arms 142 formedfof spring wiretwhich 'in general form a sharply acute trian'glewith the` base ends connected to a transverselyl extending-insiilatug strip"114. Thel center' of' this"y strip" carries" af pin 146i' vfli'ich"projec'tst'thev right and through a transverse l-ile'in the end ofthe" shaft 138 and is "there'se'curedby a set screw in'fthe end 'ofthe shaft.` At the left hand e'nd of the 'stylus' the two' "arms 142, one of which is ah'alf -inch or so longer than theother, are connected'to the'two ends of a sh'ortf strip 148J`of electrically heated resistance ribbon" which" isihorizontallyv` disposed and rests' againstl the topsurface' of the'kn'ife edge'78. Thejtwo armsorwires E42, whieh are insulated from each 'other'therefore serve bothto support the heating'element 148 and act as'the electrical leads forvconducting current throughv thissribben. Althoughiitiis Vnot lsh'ownin the drawings, the-'Tight handends ofthe wires' 140are'- soldered to flexible'pi'gtail leads which'` areA connected" to any suitable sourceof electric power at -co'rn'paratively lowvoltage.

Thesefwires or arms 142.`l` lie directly above the insulating spacerf9'4 which"connects-l the'idler roll armsf'88. Thus, when'the knob 122 is rotated Vand lifts the ar'ms188 andv spacer 94, this'V spacer will be brought against the lowersurfaces of -th'e wires142 yat ai point just' behind the resista'nc'zeV ribbon' 1,48. The? result is that theribbonr148 is"lifte'd"fr'omthevicinityof'the knife edge 78` atthe same timethat `the roller 84 ismoved well awayfrorn'fthe driving roll Si) "and 'simultaneously with the raising ofthe te'n'sionrffrom thecross pin 32.

TofloadI the-instrument with tapey therefore the roll of "tape'f is'ins'er'ted with its spool opening over the topof 'thet'detentfand with the 'inside end of the 'roll inclined d'ov'vr'iwardly.v Then as theNv outer end of` the roll is moved 'down'wardlytoay horizontal position it depresses thet-detent y30 and -slipseasilyl over the tube 26 withfthe detent 30 helddown-b'y. the inner'surface of thespool 27; The roll" is` pushed straight'inwardly untilfthe detent vroll "and the idling roll 84. The end is then passed across the table 108 beneath'the guard 112 and out of the' machine at 110. To facilitate the latter part of this operation, the guard 112 should be tilted upwardlyas prev'iouslyfexplained, and the operators'nger should be passed into' the tape opening at the lleft hand edge of the machine into the clearance space provided in the guard 112 at 118. The knob 122 is then rotated in a counterclockwise direction'so as'to lowerthe tensioner38 into position against the' pin 32 while simultaneously lowering the ribbon 148 of the stylus 140 against the portion of the tape passing over the knife edge 78. At the same Itime theidling vroll 84clamps thetap'e against the driving `roll 80. This completes the threading operation.

When the machine'is'placedin operation the driving roll 80 revolves in a counterclockwise direction thereby pulling the tape from thefroll 29 and'p'assing it tothe left and across the vtable 108 and out of the machine. Since the 'tape 29 is brought over the top of the pin 32 and thence sharply downwardly around the end 4'4' of the tensioner 38, considerable 'friction is placed upon the tape at this point. However, as the tensioner 38 israised, the friction introduced at this point will be less because the tape 29 then will be brought over a smaller portion of the circumference of the pin 32 and will make a less yksharp angle between the pin-32 and the lower end 44 of the tensioner. Therefore, by proper adjustment of the tension introduced 'into the ysystem by the springs 52, any tendency of the tape toresi'stV movement through thenachineto ltoo greatanr extent will be accompanied byT a sugar lifting of the lower end 44 of the tensiner '38. This 'arrasar by the springs 52 is exactly balanced by the amount of drag on the lower end 44 of the tensioner by the tape passing therearound. The resistance of movement of the tape through the machine or in other words, the tension effect which draws it snugly over the top of the knife edge 78 will therefore remain substantially constant even though the spool 28 changes in diameter as the tape is consumed. Further, radical changes in humidity which sometimes affect the characteristics of the tape will have very little effect upon the tension of the tape at the knife edge 78.

The tape which the specific machine here described is designed for and therefore the type which it is preferred to use is one made of paper having a white surface upon which black markings are made when heat is applied thereto. This tape forms no part of the present invention but is available and usually comprises a paper base which is colored black and upon which an extremely thin heat sensitive white surface is coated. The application of heat breaks down the surface coating and exposes the black background. inasmuch as the tape is drawn upon by the ribbon of the stylus, which slides back and forth along the area where the tape passes over the knife edge 78, it will be seen that the arcuate motion of the tip end of the stylus will be converted into a straight line marking transversely of the tape. Although photographic tape or tape which is drawn upon by a pen could be used in a machine of this type, the use of a heat sensitive tape together with the heated stylus has the advantage of providing immediate markings, thus diering from the photographic tape which has to be developed. Also it is less messy and more quick- 1y available for use than a pen and ink arrangement.

The rearward edge of the vertical plate 22 carries a bracket 150 which extends to the right and is offset somewhat toward the tape 29 and at its right hand end has a boss 152 which is drilled vertically to journal a shaft 154. This vertical shaft may be rotated from side to side and at its upper end carries a second stylus 156 which is exactly simiiar to the stylus 140. The ribbon 148 of this stylus also rests upon the portion of the tape passing over the knife edge 48, but well toward one side thereof so that the markings made by this stylus are in the margin portion of the tape beyond the central zone marked by the stylus 140. The ribbon 148 of this second stylus may be energized in parallel with the circuit which energizes the stylus 140.

This second stylus, as will be pointed out in greater detail presently, is for the purpose of indicating to the oper ator that the tape is not slipping and also which of several sets of leads are connected to the patient. In the furtherance of this marking, the .marginal portion of the tape carries numbers from l to 4 which define zones spaced successively inwardly from the edge of the tape. This is best seen in Figure 2. An examination of this figure will show a continuous line drawn through the numerals l thereby indicating that the main trace on the tape is obtained from the number l connection of the electrodes. The mechanism to be described is so arranged as to shift this line 160 automatically so that it passes through the appropriate set of of numerals depending upon the electrode connections. Since there are four sets of numerals, positioning of this line automatically takes care of four different sets of electrode connections. Occasionaily still other arrangements are used in making an electrocardiogram and a scheine of coding these additional conncctions is provided and will be described. In the interest of uniformity, this additional coding is done normally only when the line is in number 4 position.

An examination of the line 166 in Fig. 2 also shows evenly spaced pips 162. These pips are formed in a manner to be described by linkage to the driven roller 80, the

roller making two pips for each revolution. Since this roller revolves at a rate of 30 R; P. M., it will be seen that the pips are made at the rate of one each second.

8 Therefore, if the pips 162 are evenly spaced on the tape, it indicates that the tape has advanced an equal distance for each second of operation and further, the heart rate may easily be determined from the tape if desired.

The vertical shaft 154 and also the similar shaft 138 projecting from the top of the galvanometer 136 have been described as being connected directly to the stylus. This is a satisfactory arrangement but it requires that the pressure of the stylus ribbon on the tape be adjusted by springing the wires 156. In the interest of convenience in adjustment, the stylus is connected in each instance to the shaft in the following manner. By reference to Figure 5 it will be seen that the upper end of the shaft 154 above the boss 152 is divided with the two adjacent ends of the shaft connected to the two arms of a U-shaped spring metal member 164. This spring metal U-shaped piece is oriented with the U-bend toward the writing end of the stylus while the two free ends project some distance beyond the shaft 154 in the opposite direction. The two shaft members 154 may be connected to the spring metal member 164 in any suitable manner, such as by swaging. The lower arm of the spring metal member adjacent its free end is tapped to receive an adjusting screw 166 which extends through an opening in the upper leg of the U-shaped member such that, as the screw 166 is rotated from above with a screwdriver so that the thread advances into the tapped opening in the lower leg, the head of the screw compresses the Ushaped spring metal member thereby tilting the upper shaft portion 154 relative to the lower shaft portion. The effect is to raise or decrease the pressure on the writing end of the stylus. Similarly, backing off the screw lowers the writing end of the stylus and increases its pressure upon the tape.

The lower end of the shaft 154 below the bracket 150 is connected to a lever 168 which extends at approximately right angles to the stylus in a direction toward and Slightly beyond the vertical partition 22 and at its opposite end is connected by a vertical pin 170 to a link 172, which extends toward the left behind the partition 22 where it is pivoted by a horizontal pin 174 to a vertical plate 176 at a point near its upper edge. This plate 176 is in turn pivoted by a horizontal pin 178 to a vertical lever at a point below and to the left to the pin 178 as seen in Fig. 5. This and some of the last above described connections are better shown in Fig. 7 in which the left to right orientation is reverse since Fig. 7 shows the back of the plate 22. Referring further to Fig. 7, the lever 180 extends approximately vertically and has its lower end pivoted by a horizontal pin 182 to the partition 22 some distance below the plate 176.

` The extreme right hand end of the plate 176 as seen in Fig. 7 is tapered so as to form a thin extension or strip 184 vat its top edge. This extension is bent at right angles to form a tab 186 which extends through an opening 188 in the partition 22 above the motor shaft where its lower edge rides upon a cam 194i fixed to rotate with the driving roll 80. This cam is circular excepting that it has two oppositely disposed notches 192 which allow the tab 186 to drop momentarily each half revolution of the driving roll 8i). Close following of the cam by the tab 186 is insured by a coil tension spring 194, one end of which is hooked through a hole 196 in the lower left edge (Pig. 7) of the plate 176 while the other end is looped around the lower end of the vertical pin 176 which connects the lever 168 to the link 172.

Now if it is assumed that the upper end of the lever 180 is held stationary, thereby fixing the pivot pin 178, the periodic dipping of the tab 136 will pull upon the link 172. Since the link 172 is periodically jerked slightly to the right, as seen in Fig. 7, this in turn pulls the end of the lever 168 and rocks the shaft 154 in a counterclockwise direction as seen from above. The ultimate result is to cause the stylus ribbon 148 to be jerked slightly toward the center of the tape momentarily, thereby pro `the"ch`assis membersv nearstheback thereof.

som'

`thereiru'- as selen in'fFigs. 5, l and`3. The' .quarter twist 'inthis link indicated at 20'2 is simply'for thep'rpose' 4of having the rlg'hthand potriori of thelink"l lieiathori zontally while the left hand portion thereof is in avertical plane.' This'y link 200 extends almost to theV right :hand end of the mchine"and"there is pivoted by alpin 2.0'4'Vtotheirnidlpointof a horizontal le'ver 206, one end of which'is'pivo'teo4 to a vertical pin208`tixed`to one'of In' order to insure proper guidance for4 the( link"` 202, it is`provided with' longitudinal slotsl21'0 'and 212 spaced well apart which slip over'v ver'ticalk pins 214"and 216, respectively. This isibest'showii in"Fig. 3. The outer'en'd of the lever 206, tht'isth'iend toward lthe front of thez'c'ase, iS pulled toward thel left as seen in Fig. 3 by a coil spring 21S h'okedthroughathole 220"in'the lever 20'6 in aposition "i 'hat forward of'uthe' pin'204'.' V'YI'he dppOsieend of this'springis secured b'y a screwg222'x'ed'din the chassis. Theftexdericy'therefore is for the 'lever 206'tovbe swung ina'clockwise'dirction so as 'to push the' link' 20'0 toward h'lff- The' ertr'e'me' forward end of the lever266 carries' a vertical pin 224 with a small roller l226 journaled thereon as lriay'b'ese'en'in Fig,` l. 4, Thisv roller presses'a'gainst the edge o f a disc carn228dispos'edto'the left thereof and mounted Iupon the shaft 2 3'0Iof'a'rotary` tap'switch having a'khobf23'2i Thistapswitch may be moved'toany' of a nrber," ofposition's andA when so" moved serves to connect'theseveral patient leads in variouscombinations. Th'e'spe'cic switch and lcircuitufor accomplishing this is not shownsince itforrnsno part of the present invention and siiitable'circuits for" this purpose willz be'app'arent to anyone skilled in; this art. So far as" the present involitionV is concerned, it'may'be assumedthatith'eswitch, when rotatedfully' in a'clockwise direction, cornesagainst a' stop" and then wh'enrot'a'ted" in a clockwise direction, successively snapsv to positions in which the-v patients leaclsI re connected'in'combinationssimply referred tol-for con enienceas'l, 2', 3,4*an'd others beyon'd4l l When the' above switch is;backed`off againsteit's' Stop, thefportionof the calm 228 farthest fromthe; switchl shaft 2301s' brought into Contact wiuirhe'carifqilwiagrelier 226, Turisme/calibrate, position'. when the tapswifch is snapped from the calibrate position tothe Noll= position, -the rol1er'226 stillride's 'upon the portion"y of "the-roam 2,28ffa'rtlies't'froni the center of rotation off the shaft (2130.' In'these two'positlons," therefore, the" endof the lever-206 nearest tothe front of'thecase isasfa'rtoward the'ri'g'ht'as se'eninliig;` 3 as it ,ahy'coridi'tions The link 20p therefore may be considered-jasfb'eingfpnlled` to its1 farthest' right' position; By referring to Fig. 7 in which the' orientation is reverse'L- it willbe appreciated thatl thelinkv 200 there shown is pulled farthestf t the'left and that'ther'etore the upper end ofthe lever 180 isi the'farthe'st to'the left of any position'it ever assumes. This bringsy about a generali shifting of' the plate 176 andniik 112 towla'rdltneiefr (Figi 7) with a' consequent rocking' of the lei/er 168' and shaft' 163` inlv a" clockwise direction as seen fromabove, which swings the stylus "1.'56 and ribbep' 14s arriedtherby te the p0sifio'frsiwwnA by Ytheline 160`inFig. 2; that iswith the line' drawn'near'est to theV edge of the tape-and so as to pass through'numer'als 1. This indicates to' the operator, therefore, that the 'patients' electrodes ar'econ'necitedy inthe Nofl manner.

When-the tap Aswitc'h'2'32' is snapped to the-No. 2l position, thecam 228`is`shifted in aclockwise direction slightly so asfto'causetheroller 226 to drop 'against a portion of the` caniVV indicated' by the' numeral 234 which is* closer toth'e tap switch shaft 230. This causes the Aforward end 4ofthe shaft'206' to be'moved somewhat tothe left, as

seen in 4Fig. v3, ,thereby carrying along with it the link 200 'and thelikage 'cnnetdtheretd an'djust dsctib'ed incdhetion' withtl're'iN.,` rpsitin Ultimately this causes the stylus ribho'nf148 to'b'e'shifted inwardly'rsoniewhat so` as'to d r'aw'itsllne through the numerals .2.. Additional'iriw'ard step's"`236 and 238 0n the'car (Fig.VV 6) permit the cani'follower 226 to" moveiin'wardly tothe No. 3an`dv No.A 4 positions as thefrotary'tap switch is swung tol the No. 3 and No. 4 electrode combinations. This`in"tnrrrcauses the' stylus to draw" itsI line through the Nos'.`3'o'r Nos. 4. The shape' of tl1`e`c'am 228 is such that beyond thepoint238,thev cam`sfce is circular so that as the tap. switch is moved beyond theNo. 4 position, no movement of the vstylus takes place. Conveniently, however, the cam surface can have an abrupt rise at 240 toserve asa stop to' limit'rota'tion of the cam when this'abrupt rise is brought against'the roller 226. i

From the above, it'will be'seen that theftape `is`.au'tomatically coded 'forany combination of leads from" 1.to4. Additional coding beyondthe No. 4 position is' accomplished as follows, it `being Yobserved that the stylus position for combinations beyond the No. 4 position i's" such as to draw thelirieI through the numerals '4., If desired, of course, an additional step, on the cam could be used for shifting the stylus into a blank position inwardly of the n'ilr'nerals 4 on the tapel although no sui'c'ient advantage in doingthis appears to justify such a provision. By referring to yFigure 7, it willbe seen thatl the leftY hand upper'f end of the plate176`is provided with a tab' 242 which would eic'tendy straight upwardly excepting thatit is 'bent'over at'ri'ght angles so as toA forma fiat'horizontal striker surface extending' away from the partition 22. Directly'abovev the striker sur'face242 the cover plate of the instiurrrentl carries a downward extending tblar member244 which` houses a push rod 246, a portion of which Vextends above the upper end of the vtubular lmember 242 to serve as a push button. The push rod y246 is somewhat lshorten'thanm theinside length ofthe tubular ymember-"244, the'iloweifend of which has an inwardly ex tendinglshoulder 248n through'which a sten`1`2'5'0,-srnaller in diameter'lthariithepush'rodl246, extends. Below the shoiilder'248v the stem`250`isprovded with a head 252 y so as tcforithaA second'shoulder which is brought against the' lower endofthe" tube'244 by a coil spring-254 housed within thei'lowervportion'o'f the tube. -One endl of this coil spring` bears: against 'the' shoulder 248 while the'. other endy presses upwardly against the lower end of the'push rodA 246`nt`of which the"v upper e`n`d ofthe stem 250 is threa'de'dl- 'The lower end of the head 252 of the. stem 250v` isv disposedl just above'thelhorizontal striker surface plate'17`61in' aclockwise direction, thereby causing pips 162wl'1`ichpoint inwardly on the tape, momentarily depressing-the button 246 will similarly cause pips pointing outwardly.'

If the operatorltherefo're has taken all of the electrocafdiog'rams that he' desiresI withthe electrodes connected in positions 1; 2, 3 andiil andjwishes to take an additional Y reading with some further' combination ofrelectrodes, he

simply moves' the rotary tap switch beyond the No. 4 position into aspo'sition giving a known' combination of elec tr'odes which isY desired and then codes this particular connection by depressing tl'lebutton 246 momentarily accordingtoany code-Tof hisownf choosing. In other words; he

y the lever 206.

`r.more ,lon g dashes which to him will signify whatever combination of'electrodes is being used.

As to details of mechanical construction, it will be seen by referring to Fig. l that the lever 206 is comprised of two strips arranged one above the other with the link 200connccted between them. The two links 206 also embrace the two faces of the roller 226 previously mentioned, which is of smaller diameter that the width of inasmuch as the cam 228 is somewhat thinner than the roller 226, a portion of the edge of the cam 228 is overlapped on its top and bottom faces by the edges of the two strips 206. The roller 226 is therefore prevented from slipping of the face of the cam 228. Also,

the pull upon the end of the link. 200 by the pin 204 is in alignment with the center of the roller 226, inasmuch as the strips 206 lie above and below the link 200 as well as above and below the roller 226. There is, therefore, no tendency for looseness of either of the pins 204 or 224 to permit detlection or bending of either to the side which could cause the position of the stylus ribbon 148 to give an inaccurate reading.

The driving roll 80 has been generally described and its use in the combination indicated. It may be formed and arranged in any suitable manner but the specic design used in the present apparatus is illustrated in Fig. 4. Here it will be seen that the shaft 258, which extends from the electric motor and reduction gear drive unit 82, ex-

i tends into a sleeve indicated generally by the numeral I260. This sleeve has a cup-shaped recess 262 in its opposite end to take the outer race of a ball bearing 264. The inner rac-e of this bearing is fitted to a stem 266, the

outer 'end of which extends through the front L-shaped bracket 72 and is secured thereto by a nut 268. The

lsleeve 260 therefore is supported at its outer end by the ball bearing 262 and stem 266, while its inner end is piloted upon'the motor shaft 258.

Drive for the sleeve 260 is elected through one or more set screws 270 which extend radially through the sleeve 260 and bear against a flexible shaft 269. The exible shaft 269 is crimped to a short length of tubing 275 which s splined to the motor shaft 258. YThe result is that even though there is no perfect alignment between the end of the motor shaft and the end ofthe sleeve 260 carried thereby, nevertheless any weaving at this point will not loosen the driving connection between the sleeve and the motor shaft since the drive is transferred to the sleeve through the flexible shaft 260. This sleeve is covered by a soft composition rubber coating 272 which forms the driving surface for the tape-and this coating is relieved as at 271 over certain circumferential portions of its area in order to permit tabs 2'73 formed at the end of the table 108 to be curved upwardly in the spaces provided by these relieved areas which prevent the tape passing rearwardly beneath the driving roll rather than across the table where it belongs. The circumference of the extreme inner end of the sleeve 260 is formed -to provide lthe cam surface 190 previously referred to. Longitudinal position of the roller 80 on the shaft 258 is effected by means of a pair of C-shaped split rings 274 and 276 which are in face to face relation, one of these rings being snapped into a groove on the shaft 258, while the other ring 274 similarly snaps into a groove in a cup-shaped recess in the inner end of the sleeve 260.

in order to line up the ribbon 148 of the stylus 156 at the proper starting position so that it will trace its line through the appropriate numerals at the margin of the tape, it may be necessary to shift `the stylus slightly from side to side to achieve proper positioning. This is facilitated by the connection between the stylus shaft 154 and 'the lever 168 which has previously been ydescribed as connected there-to. The lever 168 is slotted as at 280 from the end with the hole which embraces the shaft 154 almost lto they opening at the other end which receives thev` pin 170. The portion of the lever 168 which embraces the shaft 154 is therefore springy and forms a light friction t therewith. The degree of friction between the lever 168 and the shaft 154 is adjusted by a clamping screw 282 which extends transversely through the two arms of the lever at approximately its mid-point. By tightening this screw the -two arms embracing the shaft 154 may be squeezed ltogether so as to achieve any degree of friction desired.

Normally the screw will be adjusted until it is tight enough to insure that no relative movement between the stylus shaft and the lever 168 will take place unless the stylus is grasped at a point close to the shaft 154 and twisted with the intention of purposely causing slipping between the shaft 154 and the lever 168.

lAlthough the operation of the apparatus forming the subject matter of this invention has been described in detail as seemed appropriate along with the description of the various components, a brief general description of its operation will now be given.

When it is desired to place the apparatus in operation the detent 30 is depressed and a roll of tape slipped over the end of the tube 26. When the roll is in position the detent will snap outwardly and prevent the roll from being withdrawn accidentally. The knob 122 is then rotated in a clockwise direction as far as it will go, thereby moving the idling roll 84 away from the driving roll 80 while simultaneously lifting the styluses `156 and 140 out of the way of the tape path. At this time also the tensioner 38 is raised away from the pin 32.y

When the knob has been rotated all the way in the clockwise direction, it will remain locked in this posiiton. The tape is then led from the roll, over the pin 32, up through the `slot 49, over the top of the knife edge 78, down between the driving roll and idling roll 84, across the table 108, and out of the machine at 110. This is donel With the guard 112 in raised position. With the tape thus placed, the knob 122 is rotated in the counterclockwise direction so as to bring the idling roll 84 against the tape opposite the driving roll 80 while simultaneously lowering the tensioner 38 and styluses 140 and 156. Preferably then the motor 82 is switched on by whatever means is provided and run for a period long enough to permit the tape to center itself in the driving mechanism. The lead selector switch 232 is then rotated as far as it will go in counterclockwise direction and the ribbon 148 of the stylus 156 is then checked to make sure that it is'drawing its line through the numerals 1. If not the stylus is grasped near the stylus shaft 154 and sprung one way or the other, thereby slipping the clutch connection between the lever 168 and the shaft 154 until proper positioning is achieved. If either of the styluses is not bearing against thev tape with the proper pressure, the adjusting screw 166 of the particular stylus is rotated one way or the other to achieve this adjustment.

From this point onward `as the machine is in operation the stylus ribbon 148 will draw a line through the appropriate set of numerals 1 to 4 to indicate the l to 4 positions of the tap switch knob 232 which in turn selects certain combinations of electrode connections to whichthese numbers are assigned. If any connections of electrodes in addition to those represented by the numerals l to 4 are desired, the tap switch knob 232 is turned tothe appropriate position and additional code markings are made upon the tape by depressing the button 246 to form the desired number of outwardly directed pips inthe line drawn by the stylus ribbon 148.

Meanwhile rotation of the driving roll 80 will be accompanied by the formation of inwardly directed pips in the line drawn by the stylus ribbon 148 at the rate of one pip for each half revolution which in the present instance is one pip each second since the driving roll rotates at 30 revolutions per minute. While the instrument is operating, the galvanometer 136, which is connected to the electrocardiograph amplifier will, through 13 the medium of the stylus 140, draw the characteristic electrocardiogram upon the central portion of the tape Where it may easily be correlated with the trace drawn by stylus ribbon 148.

Although our invention has been described in connection with -a specific embodiment thereof, it will be appreciated that additions thereto and variations therefrom may be made without departing from the scope of the invention.

Having described our invention, what we claim as new and useful and desire to secure by Letters Patent of the United States is:

1. in an electrocardiograph, the combination of a tape roll support, two coacting tape tensioning elements adapted to engage opposite sides of tape trained therebetween from said roll support, means supporting one of said elements for movement toward and away from the other element, -a thin elongated tape support for tape trained from between said tensioning elements, a exible stylus extending into proximate opposing relation to said elongated tape support, a rotary tape pulling roller, driving means connected to rotate said roller, a tape clamping roller for holding against said pulling roller tape trained from said elongated tape support; a roller support lfreely swingable relative to said stylus, said elongated tape support, and said tensioning elements and connected to support said clamping roller; means pivotally supporting said swingable roller support, said pivotal support means and the coacting portion of said swingable roller support being formed to provide for translation of the swingahle support, stationary guide means, 4guide means on said roller support positioned for separable engagement with said stationary guide means, said stationary guide means and said roller support guide means being oriented to -constrain said clamping roller in the vicinity of said pulling roller lfor movement toward the latter in a predetermined direction making Ia large acute angle with a line extending through the axes of both rollers, a spring connected to the roller support to urge the latter in a direction for carrying said clamping roller toward said pulling roller, said spring being oriented to have a line of action on the roller support which mak-es lan acute angle with said predetermined direction, a rotary disabling cam having a manual operator therefor, a cam follower on said roller support positioned for engagement by said cam to translate and swing said roller support to a tape threading position in which said clamping roller is carried away from said pulling roller, means on said roller -support positioned to move said stylus away from said elongated tape support as an incident to movement of said roller support to said tape threading position, `and means intercon nesting said cam with said one tape tensioning element to move the latter away from vthe coacting tensioning element as an incident to operation of said cam to separate said rollers.

2. in an electrocardiograph, the combination of -a tape roll support, tape tensioning means adapted to engage tape trained from said roll support, a thin elongated tape support for tape trained from said tensioning means, a rotary tape pulling roller, driving means connected to rotate said roller, a tape clamping roller for holding against said pulling roller tape trained from said elongated tape support, 'a support freely swingable relative to said elongated tape support and to said tensioning means and connected to support said clamping roller, means pivotally supporting said swingable roller support, said pivotal support means and the immediately coacting portion of said swingable roller support lbeing formed to provide for translation ofthe latter, stationary guide means, guide means on said roller support positioned for separable engagement with said stationary guide means, said stationary guide means and said roller support guide means being oriented to constrain said clamping roller in the vicinity of said pulling roller for movement toward the latter in a predetermined direction making a large lacute angle with a line e'xtending through the axes of both rollers, a spring connected to said roller support to urge the latter in a direction for carrying said clamping roller toward said driving roller, said spring 'being oriented to have a line of laction on the roller support which makes an acute angle with said predetermined direction, a rotary disabling cam having La manual operator therefor, and a cam follower on said roller support positioned for engagement by said cam to translate and swing said roller support to a tape threading position in which said clamping roller is Icarried Iaway from said pulling roller.

3. In an electrocardiograph, the combination of a tape roll support, tape tensioning means adapted to engage tape trained from said roll support, a thin elongated tape support for tape trained from isaid tensioning means, a rotary tape pulling roller, Idriving means connected to rotate said roller, la tape clamping roller for holding against said `pulling roller tape trained from said elongated tape support, a support freely swing-able relative to said elongated tape support and said tensioning lmeans and connected to support said clamping roller, means pivotally supporting said swingable roller support, said pivotal support means and the immediately coacting portion of said swingable roller support being formed to provide for translation of the latter, guide means coacting with said roller support to constrain said clamping roller in the vicinity of said pulling roller for movement toward the latter in a prede-termined direction making a large acute angle with a line extending through the axes of both rollers, 'a spring connected to -said roller support to urge the latter in a direction for carrying said clamping roller toward said driving roller, and leverage multiplying means including a manual operator therefor coacting with said roller support to move the latter to a tape threading position in which said clamping roller is carried Aaway from said pulling roller.

References Cited in the ile of this patent UNITED STATES PATENTS 745,240 Rolland Nov. 24, 1903 1,400,827 Leumalm Dec. 20, 1921 1,910,361 Pick May 23, 1933 2,133,104 Logan Oct. 1l, 1938 2,152,333 Spitzglass Mar. 28, 1939 2,511,195 Buhrendorf et al June 13, 1950 2,530,739 Stamper Nov. 2l, 1950 2,575,959 Hogan Nov. 20, 1951 2,590,554 Lukacs Mar. 25, 1952 

